Study shows leaking wells, not fracking, causes tainted water

Based on a new study, it wasn't fracking that caused contamination of groundwater in Pennsylvania and Texas. It was leaky pipes and cement casements transporting the methane gas to the surface that caused the tainted water.

According to a recent study published Monday in the Proceedings of the National Academy of Sciencs, The actual fracking procedure itself is not the cause of recent contamination of groundwater in the states of Texas and Pennsylvania, two of the biggest drilling regions in the country.

Critics have long maintained that fracking, the process of forcibly pumping large volumes of water, sand and chemicals deep underground to crack open deposits of oil and gas, was responsible for methane contaminated groundwater in those areas where fracking took place. Scientists speculated that methane, loosened by fracking migrated from deep underground and up into the aquifer, tainting the water.

But researchers from Duke, Stanford, Dartmouth and the University of Rochester studied the gas content of 133 drinking-water well sites over a period of two years from 2011 to 2013, tracing precisely how the methane gas migrated into the wells. They found that the gas escaped as it traveled vertically up through the pipes, leaking through the cement casements and into the aquifers.

"These results appear to rule out the migration of methane up into drinking water aquifers from depth because of horizontal drilling or hydraulic fracturing, as some people feared," researcher Avner Vengosh, a professor of geochemistry and water quality at Duke, said in a statement.

"We found the evidence suggested that fracking was not to blame, that it was actually a well integrity issue," said Ohio State University geochemist Thomas Darrah, lead author of the study. Calling the results of the study "good news." he went on to say this type of a contamination problem is easy to fix and should be more preventable.

The scientists, using noble gas and hydrocarbon tracers, analysed the gas content of the wells in two states. They found eight clusters of wells, seven in Pennsylvania and one in Texas. The Pennsylvania wells showed increased levels of natural gas from Marcellus shale. Wells in both states showed contamination by natural gas from shallower intermediate layers of shale.

In four of the affected clusters, the researchers' noble gas analysis showed that methane gas from the well drilling sites was escaping from shallow depths because of faulty or insufficient rings of cement that are supposed to surround the gas well shafts. In three clusters, tests showed the methane was leaking through faulty well casings, and in one cluster, the escaping methane gas was linked to a well failure.

“People’s water has been harmed by drilling,” said Robert B. Jackson, professor of environmental and earth sciences at Stanford and Duke. "In Texas, we even saw two homes go from clean to contaminated after our sampling began."

The use of noble gas and hydrocarbon tracers in combination is an unique way of identifying and distinguishing between the signature of natural methane and any stray gas contamination from shale gas drill sites. “This is the first study to provide a comprehensive analysis of noble gases and their isotopes in groundwater near shale gas wells. Using these tracers, combined with the isotopic and chemical fingerprints of hydrocarbons in the water and its salt content, we can pinpoint the sources and pathways of methane contamination, and determine if it is natural or not,” said Darrah.

CITATION: “Noble Gases Identify the Mechanisms of Fugitive Gas Contamination in Drinking-Water Wells Overlying the Marcellus and Barnett Shales,” Thomas H. Darrah, Avner Vengosh, Robert B. Jackson, Nathaniel R. Warner and Robert J. Poreda, published the week of Sept.15, 2014, in the Proceedings of the National Academy of Sciences. www.pnas.org/cgi/doi/10.1073/pnas.1322107111